Quantum Monte Carlo Simulations of the 2D Su-Schrieffer-Heeger Model

Over the past several years, a new generation of quantum simulations has greatly expanded our understanding of charge density wave phase transitions in Hamiltonians with coupling between local phonon modes and the on-site charge density. A quite different, and interesting, case is one in which the phonons live on the bonds, and hence modulate the electron hopping. This situation, described by the Su-Schrieffer-Heeger (SSH) Hamiltonian, has so far only been studied with quantum Monte Carlo in one dimension. Here we present results for the 2D SSH model, show that a bond ordered wave (BOW) insulator is present in the ground state at half filling, and argue that a critical value of the electron-phonon coupling is required for its onset, in contradistinction with the 1D case where BOWexists for any nonzero coupling. We determine the precise nature of the bond ordering pattern, which has hitherto been controversial, and the critical transition temperature, which is associated with a spontaneous breaking of Z(4) symmetry.

Automated summary

A new generation of quantum simulations has expanded our understanding of charge density wave phase transitions. The SSH Hamiltonian describes a scenario where phonons exist on bonds and modulate electron hopping. Results for the 2D SSH model show the presence of a bond ordered wave insulator at half filling, with a critical value of electron-phonon coupling required for its onset.